[Gang - This post was made circa April-May 2000 on QRP-L mail list by Ed WE6W; it is used with Ed's permission......73, monty N5FC] ---- WE6W Resonant Speaker---- Materials 4 Inch diameter sphere with 2 inch diameter hole in It 1 inch diameter speaker. 6.5 inch length of 2 inch I.D. PVC pipe. 2.65 inch length of 1.1 inch I.D. PVC Pipe. wood disk 0.25 thick, 2 inch Diameter with hole in center for 1.1 I.D. PVC pipe. Note PVC diameters, inside and out, are VERY Variable. Measure and trim your work accordingly. OPTIONAL Tuning Plunger for rear sphere 0.75 inch hole in sphere, 90 degrees from 2 inch hole. 6 inch .75 S.D. metal tube. Plunger is 6 inch metal or wood rod with wood and foam or teflon piston screwed/epoxied to end. Expand teflon by tightening two nuts, one on each side of Teflon and threaded end, by tightening. if using wood discs, add 1 inch cylinder of foam around shaft to support the plunger and provide necessary friction. Attach wires to speaker and run wires into sphere and out of small hole at rear of sphere (directly opposite speaker) Mount speaker about .1 inch inside sphere opening. The face of the speaker is 0.1 inch back of the plane of the opening. The speaker is firing outt of the sphere. Heat a needle and push 4 holes Into speaker plastic rim and attach small buss wire. Punch holes into lip of sphere opening and tie off wires firmly. Glass or metal spheres require some ingenuity for mounting the speaker. Speaker is now suspended and centered in sphere opening, with the outward firing speaker about 0.1 inch from the plane of the opening and inside the sphere. There is a volume of air around the speaker edges. Do not close this area off. Epoxy or tape sphere to 8.5 inch PVC pipe so speaker fires Into pipe. Performance requires all joints be aIr tight. (Tuning plunger included). Press-fit or epoxy 0.75 O.D. metal tube to other hole in sphere. Add plunger assembly now or later. Using metal ruler and permanent marker, measure from the remaining opening in 8.5 inch tube and make a mark at 4.25 Inches (The center) of the inside of the tube. Slide the 2.65 inch tube into the wood disc and center the tube with about 1.2 inches of tube on either side of the disc. Epoxy tube in place or tape the tube so it won't slide in/out of the disc. Slide disc/small tube assembly into the big tube and just past he 4.25 inch mark so you can see the mark made previously.. The disc should fit snugly but should be movable for tuning. Connect speaker to radio or audio source. Adjust audio source level and frequency to your desired tone. Peak the resonant speaker by sliding disc/small tube assembly in/out of the larger tube by no more than 3 inches either side of center. I used a metal hook tool. The hook passes thru the small tube and you can pull the disc assembly out, or you push the assembly in using two tools or gradually rocking the disc with one tool. After peaking the desired tone, now you adjust for best cut-off and bandpass using the rear plunger if you installed it. Set plunger all the way out and just covering the end of the metal pipe. Set signal source about 100 Hz ABOVE desire tone set previously. Adjust rear plunger to null this tone. Recheck desired tone and peak with disc as before. You will have lots of fun experimenting with different frequencies and bandpass characteristics. It is especially exciting to tune the plunger and hear the radio QRN disappear. Note, this speaker has approximately +/- 45 HZ bandwidth. is approximately 4 dB over typical radio speaker and the signal/noise improvement is approximately 12 to 20 dB depending on construction materials and quality of construction of the device, That is it. Enjoy your WE6W resonant speaker. (c) 1999 Ed Loranger mailtowe6w@qsl.net Permission to copy and distribute granted for non-profit use only. -Ed AR QRP Millennium QSO's=560/2000 72, Ed WE6W, A-i OP; http//www.qsl.net/we6w Santa Rosa, CA QRP-Z#106 QRP-L#lc6s AR#112 NC42227 ARCI#.9397 ARS#275 >from we6w@qsl.net Wed Apr 14 200516 1999 Subject Re: Resonant Speaker project Hi gang, I corrected some spelling errors (2), and I have some clarity regarding the sphere. Maximum 4 inch I.D. HOLLOW sphere. Plastic, metal glass etc. Sources include XMAS ornaments, light diffusers from a vanity, I even used a 60 watt light bulb, standard G.E., that was set in epoxy and another in concrete. I made a quick stand for the device by using a 4x4 Inch by 2 Inch piece of rigid packing foam. I cut a 2 inch or so diameter hole in the foam and slipped it over the big tube. Also, I build a wood stand that was nice. A close friend made a real fancy stand out of cherry wood. ONE CAUTION A sudden strong signal can bottom out the little 1 inch speaker. Good luck finding a I watt speaker of that size.. So watch the speaker drive when operating thIs device. Wishing you all the best of %n using it. 72/ Ed Loranger we6w/6 -Ed AR QRP Millennium QSO's--560/2000 72, Ed WE6W, A-l OP; http//www.qsl.net/we6w Santa Rosa, CA QPP-z#106 QRP-L~ 068 AR#,112 NS#2227 ARCI#9397 ARS#275